新疆楼兰地区雅丹地貌差异性侵蚀特征

Erosion Characteristics of Yardangs at Loulan Area,Xinjiang,China

楼兰地区雅丹地貌正处于活跃发育时期,为研究雅丹地貌侵蚀作用提供了良好的载体。对楼兰雅丹地层岩性、地貌形态特征等进行野外调查、测量,进行室内试验、分析。结果表明:楼兰雅丹地层形成于全新世时期,主要由较为坚硬的黏土粉砂层(CS)和松散的砂质粉砂层(SS)两类组成,并且CS层和SS层交替出现。这导致雅丹体出现显著的差异侵蚀现象。由于地层存在差异侵蚀,楼兰雅丹侵蚀较慢的CS层普遍出现岩层坍塌现象,CS层坍塌块体长度(L)和厚度(T)分别代表了SS岩层的相对侵蚀深度和CS层的厚度。统计结果显示楼兰雅丹CS层坍塌块体长度和厚度存在中度正相关关系(R=0.553)。但是,随着坍塌块体厚度的增加,其长度增加呈减缓趋势(L/T比值逐渐减小趋势),直至长度和厚度相等(L/T≈1)。综合分析表明,楼兰地区雅丹地貌发育主要受风蚀作用影响,但是区域地层岩性特征、重力作用对楼兰雅丹侵蚀起着特殊重要影响。

The Yardangs at Loulan area are in an active development period.This is beneficial for the study of their erosion characteristics.Based on the field investigation and measurement of the geomorphologic shape,and the laboratory experiment,the results are shown as follows.The stratum of the Yardang landforms at Loulan area is formed during Holocene,which are comprised of solid clayey-silt layers(CS)and unconsolidated sand-silt layers(SS)alternately.The landform has suffered different erosion rates,which corresponds to the different stratums.The solid CS layers have left more residual because of more anti-wind erosion,and collapsed at last.The length(L)and thickness(T)of the collapsed blocks delegated the erosion depth of SS layers and the thickness of CS layers respectively.The statistics reveal that Land Tof the collapsed blocks have moderate positive correlation(R=0.553).But the L lengthens slowed down as the Tincreases(the ratios of L/T decreases)until to L/T≈1.Comprehensive analysis indicates that the development of the Yardang landforms is mainly controlled by the wind.But the lithology and gravity also play important roles.